1. Field of Invention
The present invention relates to a flat panel display and, more particularly, to a capacitor of a flat panel display.
2. Description of Related Art
The flat panel display consists of several pixels. Each pixel comprises a pixel electrode and a thin-film transistor (TFT) connected to the pixel electrode. A signal line transmits signals to the TFT to turn on/off the TFT. After the pixel electrode provides the voltage, the TFT is turned off until a scan line turns on the TFT at the next time, so that the voltage can be rewritten into the pixel electrode or removed from the pixel electrode.
However, to maintain the previous voltage written in the pixel electrode prior to second time the scan line turns on the TFT, the storage capacitor (Cst) is needed to enlarge the whole capacity so that the voltage written in the pixel electrode can last longer. The power stored by the storage capacitor is directly proportional to the areas of both the anode and the cathode of the storage capacitor, and is inversely proportional to the distance between the anode and the cathode.
However, continuous improvement in the resolution of the screen results in a corresponding reduction in the pixel size. In order not to affect the aperture ratio, the area of the storage capacitor needs to be compressed which lowers the capacity. In addition, the storage capacitor manufactured by the conventional process, the thickness of the dielectric layer must be greater than 3000 Å and this will limit the storage ability of the storage capacitor to store power. Therefore, it is an important issue to enhance the capacity of the storage capacitor so that the image stabilization of a pixel could be maintained.